Braking collar for hinged beater arms of a hammer mill, used especially for grinding of fuel

ABSTRACT

A braking collar consisting of inner and outer segments, which under the action of centrifugal force, are pressed against projecting lugs of the beater arms of a hammer mill and thereby apply a braking force to the swinging rythmic movement of the arms.

United States Patent Loevenich I BRAKING COLLAR FOR HINGED BEATER ARMSOF A HAMMER MILL, USED ESPECIALLY FOR GRINDING OF FUEL [75] Inventor;.Iosel Loevenich.l.everkusen Germany [73] Assignee: Babcock & WilcoxLimited, London,

England [22] Filed: Oct. 5, I973 [2]] Appl, No.: 404,056

[52] US. Cl. 241/194 [5|] Int. Cl. .7 B02c 13/04; B02c l3/06 [58] Fieldof Search t. 24l/l94 [4 1 Apr. 29, 1975 [56] References Cited FOREIGNPATENTS OR APPLICATIONS l,l34.570 8/1962 Germany 24l/l94 PrimaryExanu'ner-Roy Lake Assistant ExuminerE. F. Desmond Attorney, Agent, orFirm.l, M. Maguire [57] ABSTRACT A braking collar consisting of innerand outer segments, which under the action of centrifugal force. arepressed against projecting lugs of the beater arms of a hammer mill andthereby apply a braking force to the swinging rythmic movement of thearms 3 Claims, 6 Drawing Figures PATENIEDAFRZSIIEYS SHEET 2 BF 2 BRAKINGCOLLAR FOR HINGED BEATER ARMS OF A HAMMER MILL. USED ESPECIALLY FORGRINDING OF FUEL BACKGROUND OF THE INVENTION The invention pertains to abraking collar used to prevent rhythmic movement of beater arms withattached beater heads. that are swingingly arranged in a beater mill.that is used especially for grinding of fuel. The braking collarconsists of inner and outer segments which, under the action ofcentrifugal force. are pressed with their outer strips of cylindricalsurface of the outer segments against projecting lugs on the beaterarms.

In such type of hammer mills it is necessary to avoid resonancevibrations of the beater arms during the rotation of the beater shaft.It is also necessary to avoid large swings of the beater arms duringstart up and shut down of the hammer mill. The vibration and swingingcause severe wear on the hinge pins of the beater arms. in the pivotholes of the hub rings of the beater shaft and in the eyelets of thebeater arm, which inevitably must lead to a breakdown of the beatermill. It is already known (German Pat. No. l.l34.570) to provide in abeater mill a braking collar consisting of inner and outer segments.having a radial surface and strips of inner and outer cylindricalsurfaces. The staggered parts of the segments surround the beater armson both sides in a fork-like fashion. Under the action of thecentrifugal force the segments press against the projecting lugs on thebeater arms and thereby reduce or eliminate the resonance vibrations. Ofcourse. there are gaps between the inner segments and between the outerseg ments in a radial-axial direction. Small vibrations of the beaterarms during rotational movement can be subdued by the frictional forcesbetween the lugs and the outer segments. However. during start ups andshut downs of the beater mill. the beater arms experience continuouslystrong swings (due to inertia) within these gaps. As a result.especially during frequent start ups and shut downs, the segments arepushed together and a large gap is formed which grows larger to itsmaximum slack. especially during opposite swings of two neighboringbeater arms. so that the lugs of the arms slip-off the edge of the outersegment. causing the outer segment to fall out. This results in anoperating disturbance that could lead to destructions inside of thebeater mill.

SUMMARY OF THE INVENTION This invention intends to improve the design.It has as an aim to provide a brake collar which has no gaps between thesegments in the circumferential direction during the rotation of thebeater shaft. and in which the stop lugs projecting from the beater armscan not move beyond the edges of the outer segment even at maximumpossible slack.

According to this invention the problem is solved by avoiding theradial-axial plane between the outer segments and between the innersegments. The invention provides on each outer segmental plate twoslanted surfaces. that are flat and rectangular with the distancebetween them increasing rapidly towards the outside. The inner segmentalplates have corresponding slanted surfaces. that are flat andrectangular but with the distance between them decreasing correspondingtowards the outside (tapered). During the rotation of the mill the innerand outer segmental plates lock together under the action of thecentrifugal force to form two closed rings. without gaps, on each sideof the beater arm. The strips of the cylindrical outer surface of theouter segments extend in the circumferential direction so far. that atboth ends a considerable distance is available beyond the contactsurface with the lugs projecting from beater arms.

Although the outer segments have been provided with a largecircumferential length to avoid any possibility of the step lugs on thearm to slip off the outer ring segments, there is a further provision ofthe inven' tion to assure that this can not happen. In order to fix theposition of the braking collar in the circumferential direction thelinks of the outer segments protrude to the hinge pins in the hub ringsof the beater shaft, or between the eyelets of the beater arms.

The advantages of the invention consist mainly of the following. The useof slanted surface between the segmental plates adds the glidingcomponent of the centrifugal force of the inner segment to the pressureexerted on the stop lug. thus improving the braking action. Also duringcoasting of the mill at shut downs the knocking forces of the beaterarms are converted into a braking action because the outer segment.which is affected by the knocking force (when the arm hits the link), isshoved up along the slanted surface of the inner segments, thus reducingan eventual gap that could be occuring due to the reduction of thecentrifugal force action. In addition, the construction of the brakecollar is such. that radial movements of the segments are possiblewithout occurence of a gap between the segments. whereby a continuoussatisfactory contact between all the surfaces is assured. that avoidsthe wear usually occuring when previously separated parts are suddenlybrought into contact. Finally, be cause of the large operationalreliability of the beater mill constructed according to this inventionit is possible to apply considerably cheaper materials for the segments,like cast steel or cast Mechanite. Therefore. the usually used forgedsteel construction, which always require extensive supplementarywelding. can be obviated and a large saving can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS An example of the application of theinvention is depicted in the attached drawings and is further explainedbelow.

FIG. 1 shows a cross section through the rotor of a beater mill with thebraking collar in rotating position.

FIG. 2 shows a plan view from the outside of an outer segment of thebraking collar.

FIG. 3 shows a section along line Ill III in FIG. 2.

FIG. 4 shows a plan view from the outside of an inner segment of brakingcollar.

FIG. 5 shows a section along line V V in FIG. 4.

FIG. 6 shows a section along line VI VI in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I depicts a rotor of abeater mill in cross section in the rotating position. It consists of abeater shaft 1 with hub rings 2 and 3 (FIG. 6). many beater arms 4 withprojecting stop lugs 5. The beater arms 4 are hingedly connected to thehub rings 2, 3 through pins 6 inserted into the hub rings 2. 3. Thebraking collar consists of outer segments 7 and inner segments 8. Duringthe rotation of the beater shaft l the braking collar is pushed outwardsby the centrifugal force so that the outer segments 7 press so stronglyagainst the stop lug 5, that the swinging motion of the beater arms 4 ishindered or checked.

According to FIG. 2 and FIG. 3 the outer segment 7 consists of twoparallel segmental plates 9 and 10 with axial slanted rectangular flatsurfaces 9a and la and strips of outer cylindrical surface 9b and 10b.The two segmental plates 9 and 10 are rigidly connected by a fixed linkll which protrudes to the hinge pins in the hub rings of the beatershaft. in order to fix the position of the braking collar in thecircumferential direction.

According to FIG. 4 and HO. 5 the inner segment 8 consists of twoparallel segmental plates 12 and 13 with axial slanted rectangular flatsurfaces 12a and 13a. The segmental plates are rigidly connected by afixed link 14 which extends radially towards the rotor axis between thehinge plns 6 or between the eyelets of the beater arms, in order toimprove the positioning of the segments forming the entire brake collar.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A braking collar to prevent the rythmic movement of hinged beaterarms with attached beater heads of a hammer mill, especially when usedfor grinding of fuels, said braking collar consisting of inner and outersegments, the outside strips of cylindrical surfaces on the outersegments being pressed against lugs projecting from the beater armsunder the action of the centrifugal force; characterized by, therelation of the radial-axial mean plane of the external segment and theinternal segment in which the segmental plates of the outer segment haveslanted surfaces that are flat, rectangular and strongly spreadoutwards, while the segmental plates of the inner segments havecorrespondingly slanted surfaces that are flat, rectangular and taperedto the outside; the said surfaces being arranged to each other so, thatunder centrifugal action said outer surface segmental plates togetherwith said inner surface segmental plates form closed rings; and, thatthe strips of the cylindrical outer surface of the segmental plateshave, in the circumferential direction of the braking collar, anadequate length so that their two ends extend considerably beyond thecontact surface of the lugs on the beater arms.

2. A braking collar according to claim 1, wherein the braking collarprevents the rhythmic movement of hinged beater arms ofa hammer mill,the hammer mill having a beater shaft, a plurality of hub rings on theshaft and a plurality of beater arms connected by hinge pins to the hubrings, the braking collar including inner and outer segments, eachsegment having a pair of segmental plates interconnected by a link, inwhich the interconnecting links of the segmental plates of the innersegments protrude to the hinge pins in the hub rings of the beatershaft, in order to fix the position of the braking collar in thecircumferential direction.

3. A braking collar according to claim 1, wherein the braking collarprevents the rhythmic movement of hinged beater arms of a hammer mill,the hammer mill having a beater shaft connected to a plurality of hubrings and a plurality of beater arms connected by hinge pins to the hubrings, the braking collar including inner and outer segments, eachsegment having a pair of segmental plates interconnected by a link, inwhich the interconnecting links of the segmental plates of the outersegments protrude to the hinge pins in the hub rings of the beatershaft, in order to fix the position of the braking collar in thecircumferential direction.

t l i

1. A braking collar to prevent the rythmic movement of hinged beaterarms with attached beater heads of a hammer mill, especially when usedfor grinding of fuels, said braking collar consisting of inner and outersegments, the outside strips of cylindrical surfaces on the outersegments being pressed against lugs projecting from the beater armsunder the action of the centrifugal force; characterized by, therelation of the radialaxial mean plane of the external segment and theinternal segment in which the segmental plates of the outer segment haveslanted surfaces that are flat, rectangular and strongly spreadoutwards, while the segmental plates of the inner segments havecorrespondingly slanted surfaces that are flat, rectangular and taperedto the outside; the said surfaces being arranged to each other so, thatunder centrifugal action said outer surface segmental plates togetherwith said inner surface segmental plates form closed rings; and, thatthe strips of the cylindrical outer surface of the segmental plateshave, in the circumferential direction of the braking collar, anadequate length so that their two ends extend considerably beyond thecontact surface of the lugs on the beater arms.
 2. A braking collaraccording to claim 1, wherein the braking collar prevents the rhythmicmovement of hinged beater arms of a hammer mill, the hammer mill havinga beater shaft, a plurality of hub rings on the shaft and a plurality ofbeater arms connected by hinge pins to the hub rings, the braking collarincluding inner and outer segments, each segment having a pair ofsegmental plates interconnected by a link, in which the interconnectinglinks of the segmental plates of the inner segments protrude to thehinge pins in the hub rings of the beater shaft, in order to fix theposition of the braking collar in the circumferential direction.
 3. Abraking collar according to claim 1, wherein the braking collar preventsthe rhythmic movement of hinged beater arms of a hammer mill, the hammermill having a beater shaft connected to a plurality of hub rings and aplurality of beater arms connected by hinge pins to the hub rings, thebraking collar including inner and outer segments, each segment having apair of segmental plates interconnected by a link, in which theinterconnecting links of the segmental plates of the outer segmentsprotrude to the hinge pins in the hub rings of the beater shaft, inorder to fix the position of the braking collar in the circumferentialdirection.